Step 1

Preheat the oven to 425ºF.

Step 2

Pour the sweetened condensed milk into a pie dish or pan and cover tightly with aluminum foil. Place the pie dish into a large roasting pan or baking pan and fill the pan with about 1-inch of hot water.

Step 3

Bake for 1 hour and 45 minutes then whisk the sauce to smooth out any lumps before using.

Step 4

Preheat the oven to 350ºF and line to baking sheets with parchment paper or silicone baking mats.

Step 5

In the bowl of a stand mixer fitted with the paddle attachment or using a handheld mixer cream the butter and sugar for 1 to 2 minutes until lighter in color and fluffy in texture.

Step 6

Add the egg yolks, vanilla extract, and salt and mix until just combined. Mix in the flour, which will be crumbly initially, but turns into a soft dough after well mixed.

Step 7

Using a 1-inch sized cookie scoop or a tablespoon-sized measuring spoon scoop out the cookie dough and roll it into a ball. Place the ball onto the prepared baking sheet.

Step 8

Use your thumb or the back of a 1/2 teaspoon-sized measuring spoon to gently press a round-shaped depression into the cookie. Spoon 1/2 teaspoon of dulce de leche into the depression of each cookie. Sprinkle with coarse salt flakes.

Step 9

Bake for 12 to 14 minutes or until the cookies are set and the edges are slightly golden in color. Let cool for 10 minutes on the baking sheet before removing to finish cooling on a wire rack.